Papers by Keyword: Atomic Hydrogen

Abstract: In this paper, we have employed density functional theory (DFT) to investigate the adsorption mechanisms of atomic hydrogens on the sidewalls of (3, 3) single-wall carbon nanotubes (CNTs) which have vacancy defects. All the calculations were performed using the generalized gradient approximation (GGA) with the Perdew, Burke and Ernzerhof (PBE) correlation functional.Our results show that hydrogen atoms can chemically adsorb on the defective nanotube. Bonding energy of per hydrogen atom decreases with the number of adsorbed hydrogen atoms. The hydrogen atoms will enhance the electrical conductivity of the (3, 3) nanotube. Besides one hydrogen atom adsorbing on the nanotube with a vacancy defect (MVD), hydrogen atoms move towards the MVD of the nanotube.

Abstract: A major obstacle facing III-V semiconductor based metal oxide semiconductor field effect transistors (MOSFETs) is the large density of trap states that exist at the semiconductor/oxide interface.[1] These trap states can pin the Fermi level preventing the MOSFET from acting as a switch in logic devices. Several sources of Fermi level pinning have been proposed including oxidation of the III-V substrate.[2, 3] In order to minimize the presence of III-V oxides it is crucial to employ either an ex-situ etch or to use an in-situ method such as atomic hydrogen cleaning.[4, 5] Although atomic H cleaning of III-V surfaces is well known, it has never been demonstrated on InGaAs (110) crystallographic faces. Furthermore, tri-gate field effect transistors (finFETs) have recently been employed in commercially available logic chips.[6] This unique device architecture allows for a reduction in short channel effects, minimization of the subthreshold swing, and a higher transconductance.[7] The InGaAs (110) surface would be the sidewalls of a vertically aligned (001) based finFETs.[8] Therefore, it is essential to find an in-situ method to efficiently remove any oxides or contamination from the (110) surfaces that is also compatible with the (001) surface. In this study, STM was employed to determine if atomic hydrogen can be used to remove the native oxide from air exposed InGaAs (110) samples. A post clean anneal was used to restore the surface to molecular beam epitaxy (MBE) levels of cleanliness.

Abstract: Effects of additives on the semiconduction transformation of lead zirconate titanate (PZT) during atomic hydrogen charging were investigated. The results showed that the resistivity of the samples decreased by seven orders of magnitude with sixty hours of hydrogen charging in electrolytic without additives. Then with further increasing hydrogen charging time, the resistivity decreased continually, however, much more slowly. Scanning electron microscopy (SEM) showed that the surface structures of PZT were changed significantly upon atomic hydrogen charging. Sodium pyrophosphate (Na₄P₂O₇) and Na₂EDTA could effectively affect the semiconduction transformation of PZT as well as the surface structure change. Transmission electron microscopy (TEM) and XRD analysis indicated that there was no new substance formed on the surface of PZT upon atomic hydrogen charging.

Abstract: The Au electrode plated nanostructure Pd was used to study the reaction mechanism of C.I. reactive blue 19 and reactive brilliant blue K-GR with atomic hydrogen in 0.2M H2SO4 solution by the electrochemical method. The nanostructured Pd/Au electrode showed the various forms of hydrogen. Through the result of cyclic voltammetry, Tafel curve and EIS, the protonation of dye molecule could accelerate the production of atomic hydrogen and the adsorption of dye on Pd/Au electrode. The decolorization efficiency using potentiostatic polarization at -0.18V was highest than that at other polarization potential because the proportion between adsorbed dye and adsorbed atomic hydrogen on electode was optimum.

Abstract: In this contribution, we address two critical and interesting aspects from both fundamental and technological point of views, which are the polarity of ZnO and the interface reactivity and stability to hydrogen and nitrogen. The effects of atomic hydrogen and nitrogen produced by radiofrequency (r.f. ,13.56 MHz) H2 and N2 plasmas and of temperature on the optical, compositional and structural properties of Zn- and O-polar ZnO have been studied. It is found that Zn-polar ZnO is highly reactive with atomic hydrogen while O-polar ZnO is almost inert. Conversely, both polarities react with nitrogen, with the O-polar ZnO showing a larger reactivity toward N-atoms than the Zn-polarity.

Abstract: Cu has been used as interconnection and lead frame in ULSIs. However, the oxidation and contamination of Cu are not easily avoided. As a result, a thin layer of Cu2O, CuO and carbon contaminations are formed at the Cu surface and these resistances are increased. Therefore, Cu cleaning is necessary. There are some reports to remove Cu oxide layers. Chemical processes such as H2 and NH3 plasma reduction are being investigated [1-5]. These methods have the problem of the plasma damage. Lee et al. proposed Cu oxide reduction using vacuum annealing [6]. However, it seems not suitable for the ULSI process, because the heat-treatment of 400oC is necessary. Therefore, low temperature Cu cleaning without plasma assist is strongly desired. In our previous work, we proposed novel low temperature atomic hydrogen or NH3 decomposed species cleaning generated by heated catalyzer [7,8]. However, in the method it is used 100% hydrogen gas. From the view point of safety, hydrogen gas diluted below explosion limit is preferred to use. In this paper we proposed a novel Cu cleaning method by atomic hydrogen generated on a heated tungsten catalyzer using diluted hydrogen as a cleaning gas.

Abstract: Ammonia formation activity was studied on the Ru/(MgO-CeO2) catalyst loaded on a Ag-Pd hydrogen permeable membrane. The ammonia formation rate for the membrane reactor was more increased than that based on the conventional flow-type one due to the high reactivity of atomic hydrogen supplied from the Ag-Pd membrane. In addition, other on-site hydrogen generation type membrane reactor was also constructed, where the Ag-Pd alloy membrane was not only atomic hydrogen supplier but also an electrode for water electrolysis. Ammonia was effectively formed even at 373 K on this membrane reactor with the electrodeposited Ru metal powder catalyst.